Along with the protracting of the natural life, the incidence of central psychogenic diseases of studying memory and cognition dysfunction, such as infant intelligence development retardation, adult dysmnesia, and Alzheimer's disease, are increasing. The last one is especially becoming a social problem and arousing people's high attention.
Alzheimer's disease (AD) is also called senile dementia or presenile dementia. It is a kind of lethal central nervous system retrogressive disease mainly represented as progressive cognition dysfunction and memory loss. According to the latest estimation of WHO (World Health Organization), the invasion population of AD in the world now is more than 20 million. The number of the population of AD is 10% of the crowd of more than 65 years old, and is 50% of the crowd of more than 85 years old. In US, 4 million people had meek cognition trauma, another 4 million people had AD, and the sick population is dramatically increasing. In China, the population of AD is creasing gradually along with the aging society. According to the result of AD epidemiological primary survey done by Peking Union Medical College Hospital, it showed AD disease incidence is 4.2% among the people of 65 years old or more in north China. Therefore, predictably there are about 5 million AD patients in China based on that at present there are 1.3 hundred million people who are more than 60 years old in China.
The cause of AD is still not recognized clearly till now, but various basic and clinical studies proved that the memory lesion and progressive cognition dysfunction of AD is closely related to the persistent relative deficiency of acetylcholine, which is the transmitter in central nervous system. The pathophysiological research showed a lot neurons in AD patients' cerebrum were lost, together with the decrease of the concentration of various neurotransmitters in central nervous system, especially the decrease of acetycholine. The lost neurons are those in neocortex, hippocampal, basal nuclei and locus ceruleus etc. of cerebrum. The distinct hypofunction of central acetylcholine system is a main pathologic change of AD anticipation, which is also present in the whole course of the disease. Using cholinomimetic including cholinoprodrug, cholinesterase inhibitor (AchEI), selective M, N choline receptor agonist had obvious therapeutic effect on delaying the occurrence and development of AD, alleviating the memory and cognition dysfunctions.
Tacrine is the first AchEI approved by FDA for treating AD. Although it is effective, it is strictly restricted clinically because of its high liver toxicity. Both tacrine and E2020, which is approved by FDA in 1996, were called first generation AchEI.
Comparing with the first generation AchEI, the medicament only with Huperzine A as its active ingredient (the trade name is Haperzine, or Selagine) belonged to the second generation AchEI, which had high selectivity with AchE in brain and had higher safety.
The clinical trials showed that the period of administration to prevent and treat the memory and cognition dysfunction was relatively long. It would last the whole life for the patients of AD. Under the circumstance, the safety of the medicament is the most important.
So it is imminently needed a kind of medicament in the field, which has good therapeutic effect and meanwhile is more safe.